Major reasons for the success of transdermal delivery were the avoidance of first-pass metabolism and ease of use. This increases drug bioavailability in comparison to other delivery methods. Transdermal Drug Delivery Systems (DDS) can also deliver drugs at a steady rate to achieve a sustainable release, which is an additional advantage. However, transdermal drug delivery methods have their drawbacks. Most important is the fact that conventional transdermal system (TTS) technology is only suited for delivering relatively small drugs across the skin. It also suffers from slow onset, because of the outer skin barrier layer, stratum corneum, that limits the through skin drug transport.
New transdermal drug delivery methods are therefore required to drive future growth in transdermal product markets. Biological products would also profit greatly from new, non-invasive delivery technology to replace hypodermic needle injection that is the current standard. The original players in the transdermal field failed to introduce such improvements, which were then introduced by a number of innovator companies.
Broadly speaking, two different new approaches for transdermal drug delivery are currently being pursued: (1) nanoporation/minimum abrasion using a physical device, and (2) nanocarriers using lipid-encapsulated formulation. Sonoporation, thermoporation) use of very fine and short needles belong to the former; ultradeformable carriers (such as Transfersome®, Ethosomes® or fluid liposomes) are examples for the latter. Any of these can deliver small or large molecules across the skin. Some examples of transdermal delivery are described in U.S. Pat. Nos. 7,094,423; 7,049,140; 7,041,870; 7,037,499; 7,034,126; 7,033,598; 7,014,855; 6,991,805; 6,982,084; and 6,979,729.
However, there is a continuing need for an improved, disposable transdermal delivery device for effective delivery of substances in a controlled manner.